1. Chapter 1 Section 2

2. Accuracy describes how close a measured value is to the true value of the quantity measured. a.k.a “the right answer”, or the agreed upon answer (“consensus” among scientists) Problems with accuracy are due to error. Example: If a wooden meter stick gets wet, it can warp, making accurate measurements difficult to achieve.

4. 7.8 g6.7 g8.0 g8.2 g7.9 g <10%Highly precise 11-20%Acceptable precision >20%Not precise

5. 2) Precision refers to the degree of exactness that a measurement can be made, and is limited by the measuring device or instrument used  how detailed your tool can measure (least count) Example: A measurement of 1.325m is more precise than a measurement of 1.3m. calipers vs. a ruler

6. Which measuring device allows for more precision? Which one could you more correctly measure 53 mL?

7.  When using scientific instruments, measure to the least count, and then estimate the next digit.  Let’s practice. Assume both of these rulers refers to centimeters. Which has a smaller least count?  What is the length of each line?

8. A lack of precision is typically due to the limitations of the measuring device or instrument. Example: If I only have one meter stick and I want to measure the length of a city block. A meter stick was not intended to measure such large distances. Example: Trying to measure the width of a human hair with a standard ruler will yield bad data because the least count lacks the necessary precision. BUT, lack of accuracy is usually due to error.

9. 1. Random – due to the small differences in measurements being read in different trials and by different people. When data is collected from an experiment, the overall differences should be within a small range. This is an acceptable type of error. 2. Systematic – usually due to an error in equipment calibration (see examples) 3. Human error – the experimenter is doing something incorrectly (unacceptable source of error)

10.  The wet (warped) meter stick from slide 2.  The triple beam balance not being zeroed out before the experiment.  Air ventilation blowing on a digital balance.  Errors in measurements of solar radiation because trees or buildings shade the radiometer.

12. See Table 1 here for measuring long distanceshere micrometer Electron scanning microscope Walking wheel measuring “tape”